Continuous curing apparatus

ABSTRACT

An apparatus for heating and compressing an elongated article ls provided. The invention comprises the use of a plurality of individual press units which are heated; the press units are moved into heating and compression relationship with opposed surfaces of the article; each press unit is moved successively into engagement with the article and into contacting end to end relationship with the previous press unit, the units being moved relative to the surface only in a direction perpendicular to the surfaces when in contact with the surfaces; the press units and the article are moved stepwise in the direction of the length of the article; the press units are continuously maintained in contact with the article until the end of the heating and compressing cycle; with the press unit finally successively being moved out of engagement with the thus produced elongated article.

[ Dec. 18, 1973 CONTINUOUS CURING APPARATUS [75] Inventor: Hugh LorainFolkes, St.

Leonards-on-Sea Sussex, England [73] Assignee: Dunlop Holdings Limited,London,

England [22] Filed: July 20, 1972 [21] Appl. No.: 273,367

Related U.S. Application Data [60] Division of Ser. No. 45,604, June I2,1970, Pat. No. 3,714,3l7, which is a continuation-in-part of Ser. Nos.775.347, Nov. 13, 1968, abandoned, and Ser. Nov 28,290, April 22, 1970,abandoned, which is a continuation of Ser. No. 592.l3l, Nov. 4. I966,abandoned.

[ 30] Foreign Application Priority Data 3,664,797 5/l972 Sorbier 425/444X Primary Examiner-Robert L. Spicer, Jr. Att0rneyWilliam A. KnoellerABSTRACT An apparatus for heating and compressing an elongated articlels provided. The invention comprises the use of a plurality ofindividual press units which are heated; the press units are moved intoheating and compression relationship with opposed surfaces of thearticle; each press unit is moved successively into engagement with thearticle and into contacting end to end relationship with the previouspress unit, the units being moved relative to the surface only in adirection perpendicular to the surfaces when in contact with thesurfaces; the press units and the article are moved stepwise in thedirection of the length of the article; the press units are continuouslymaintained in contact with the article until the end of the heating andcompressing cycle; with the press unit finally successively being movedout of engagement with the thus produced elongated article.

4 Claims, 20 Drawing Figures PATENIED DEC 18 973 SHEET 2 BF 9 FlG.b

I FIG. 5

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PATENTEBHEB 18 ms PATENTED DEC 18 I975 sum 7 OF 9 .voN N ba 0%CONTINUOUS CURING APPARATUS RELATED U.S. APPLICATIONS This applicationis a division of my copending application Ser. No. 45,604 new U.S. Pat.No. 3,714,317, filed June 12, 1970 which is in turn acontinuation-inpart of my copending applications Ser. No. 775,347, filedNov. 13, 1968 (now abandoned), and 28,290 filed Apr. 22, 1970 (nowabandoned), the latter application being a continuation of my nowabandoned application Ser. No. 592,131, filed Nov. 4, 1966.

This invention relates to the curing of elongated articles, and inparticular to the curing of rubber and plastic belting and likeelongated articles.

The production of extremely long belting is of ever increasingimportance, being necessary for moving pedestrian sidewalks and rampswhich are being installed in increasing numbers in areas which haveheavy pedestrian traffic. Exemplary of such uses is to avoid thenecessity of forcing passengers at airports from walking from theterminal building to the departure gates and in providing upward rampsat modern sports stadiums. it will be clearly appreciated that acontinuous belt of considerable length is required for such movingsidewalks and ramps. Uniformity in these belts is most important, asvariations may result in a space between the sides of the movingsidewalk housing and the belt. in such a case, it is possible that apersons leg could become trapped, resulting in serious injury.

The method for curing elongated belting generally used in the prior artcomprises the use of large upstroke presses, usually steam heated. Amoving table is arranged to run the full length of the press and is ofheavy box section design for minimum deflection. The platens are madefrom steel plate accurately machined and polished on the workingsurfaces.

The platens are divided into a number of chests. With the exception ofthe two end chests, the remainder are inter-connected to allow efficientcirculation of steam or water. Conveniently the two end chests areisolated from the remainder, so that they can be maintained at a lowertemperature to provide for an overlap between each press charge.

It is extremely important in the prior art process that the temperatureof the platens is constant and controllable to ensure uniformity ofcure. it is also important that the belt receives uniform compressionover the whole platen area to obtain maximum adhesion of the plies andcovers, and also to produce a belt of uniform cross-section, which isessential for correct tracking of the belt in service. Without correcttracking the aforementioned dangerous problem of a gap between the beltand the side track may result.

Hydraulic gripping and stretching gear is also fitted to the press sothat stretch can be applied prior to curing to limit the amount ofelongation which will occur in service, stretch being maintained duringcuring.

The uncured belting is supported in a roll adjacent to the press and aleader consisting of a piece of cured belting is attached to the end bymeans of belt fasteners. At the same time the temperature of the pressplatens is adjusted to the required temperature.

Longitudinal molding irons (full press length) of the required thicknessto allow the necessary compression of the uncured belt are placed on thebottom platen. A sufficient number of these irons are used to form aframe to give the final width of the belt, when lateral pressure, eithermechanical or hydraulic, is applied from the sides of the press.

The end of the leader is drawn through the press to a position where thecured belt is eventually formed into a roll. 7

The first charge of the belt is drawn centrally into the press.Stretching equipment consisting of clamps fitted at each end of thepress (one being movable) are closed onto the belt and a predeterminedpercentage of stretch applied. The press is closed on low hydraulicpressure, and lateral pressure is applied to the belt edges, followedafter an interval by the application of high pressure. The hydraulicpressure, rate of application, delay and cure cycles will vary accordingto the type and grade of belt, for example, from 12 minutes at 50 psisteam for a thin belt to 48 minutes at 30 psi steam for a belt one inchthick.

At the end of the cycle the press is opened, the lateral pressurereleased and the belt is drawn through the press, leaving approximately12 inches of the end of the charge at the exit end of the press.

The process is then repeated until the required length of belting hasbeen cured.

It will be readily appreciated that there are practical difficultieswhich present serious drawbacks to the conventional method of the priorart to which no satisfactory solution has hitherto been found.

The use of a single press means that the method is essentially a batchprocess in that when any particular length of article has been cured,the press must be opened and the cured portion of the article withdrawnfrom the press, thereby drawing behind a portion of uncured materialwith the boundary between cured and uncured material being advanced tothe forward end of press before the latter is closed and the curingcycle repeated. This method is not only time consuming, but furthermoredifficulties arise in the exact alignment of the uncured portion whilewithin the press, resulting in problems of double-curing or under-curingof the end of the portions cured in each batch treatment.

A further major disadvantage of the conventional method is thatconsiderable time is wasted due to the fact that the curing process mustbe interrupted when the press is opened and not resumed until the pressis closed on the succeeding portion of uncured material. The fact thatthe prior art batch process does not allow continuous production andtherefore restricts the amount of belting which can be produced in aparticular time period, is very unsatisfactory, especially in view ofthe large capital cost of the machinery used.

Further disadvantages arise from the size and weight of the presses andparticularly, of the moving parts. In a conventional form of press,known as the column type," a typical platen size is 32 feet X 84 inches,giving an effective length of 28 feet, and an effective width of inches.In this press, the moving table is actuated by 24 hydraulic rams, eachof 15% inches diameter, and the total weight of the presses is 420 tons.Another form of press, known as the plate Frame walk-in type, has atypical platen size of 36 feet X 65 inches, giving an effective lengthof 30 feet and an effective width of 60 inches. Again, a large number ofhydraulic rams are used to actuate the moving table and the total weightof the press is 300 tons.

It will be thus appreciated that conventional presses are large, heavyand expensive items. To increase output, presses with even largerplatens have been proposed. However, the larger the press, the moredifficult and expensive it is to ensure that the platens are accuratelymachined and assembled and that uniform compression occurs over thewhole of the platen area.

An object of this invention is therefore to provide an improved processand apparatus for curing rubber and plastic belting and other elongatedarticles.

A further object of this invention to provide belting of excellentuniformity, and which can be produced with greater economy thanpreviously possible through the provision of a continuous beltingprocess.

The objects of this invention are achieved through the apparatus andmethod of the present invention. In its broadest aspect, the presentinvention provides a method of curing an elongated article, comprisingpressing the article in a press comprising a number of press units, thepress units being successively engaged with the article at a firststation and moving in engagement with the article to a second stationwhere the press units are successively disengaged and returned to thefirst station.

In a particular embodiment of the invention, on completion of a curingoperation and being disengaged from the article at the second station,the press units are employed to execute a further curing operation inthe course of returning to the first station. The further curingoperation may comprise transfer of the press units to, and successiveengagement of the press units with, an article at a third station andmovement of the press units in engagement with this article to a fourthstation where the press units are successively disengaged andtransferred to the first station.

To avoid gaps between cured portions of the article, the press units aremoved into contacting end to end relationship, and also the movement ofthe press units, relative to the article, is in a directionperpendicular to the surface of the article once the press units are incontact with the article.

When curing certain articles of a plastic consistency, it has been foundthat as a press unit is moved into contact with the article, a smallamount of material forming the article is pushed out at the reat edge ofthe unit. The next press unit has to compress this extra material and asa result more material is pushed out at the rear edge of this next unit.This action become progressive.

By moving the press units into contact with the article in a particularmanner, expulsion of material can be avoided. Thus according to afurther embodiment of the invention, pressure is applied by the pressunits to successive contiguous portions of an elongated article to becured, the pressure exerted on each portion of the article by itsrespective press unit initially substantially greater in the region ofthe forward end of the said portion of the article than in the remainderof that portion of the article. Pressure is then applied or increased inthe remainder of that portion of the article in a progressive mannerfrom the forward end to the rearward end thereof, the pressure beingapplied or increased in the region of the rearward end of the saidportion of the article substantially simultaneously with the initialexertion of pressure in the region of the forward end of the nextfollowing contiguous portion of the article.

The invention can be used for curing articles other than belting andlike material. Thus the invention can be used in the manufacture oflaminated material, such as plywood, and boarding such as fibre-board,insulating board and other products which require pressure and heattreatment during production.

In this specification the term curing, and derivatives thereof, refersto heat treatment to produce a change of state and specifically inrelation to rubber and similar materials refers to vulcanisationthereof. A further example is the application of pressure and heat toconvert material in one form into another, as for instance to convert apasty or liquid material to a solid self-supporting form.

Various embodiments of the invention will now be described by way ofexample, in conjunction with the accompanying diagrammatic drawings, inwhich:

FIGS. 1 to 4 are plan-view representations of a sequence of successivesteps in the curing of two lengths of conveyor belting in two parallelpresses;

FIG. 5 shows a transverse cross-section through a continuously heatedpress unit, having its own compressive force-applying means, inengagement with an article being cured;

FIG. 6 shows a section of the line VI-VI of FIG. 5;

FIG. 7 shows a longitudinal cross-section through part of two adjacentpress units of the type shown in FIGS. 5 and 6, each having its owncompressive forceapplying means;

FIG. 8 shows a transverse cross-section through a press unit designedfor intermittent heating and for use with fixed presses;

FIG. 9 shows a longitudinal cross-section through part of two adjacentpress units of the type shown in FIG. 8 showing the platens clamped endto end;

FIG. 10 shows a vertical cross-section through a single daylight fixedpress having re-heating means in the form of hot plates, for the platensof the press units, a press unit being shown in position;

FIG. 11 is a plan view representation of a stage in the course ofcontinuous curing of two conveyor belts side by side at the same level,employing single daylight fixed presses;

FIG. 12 shows another plan view of two curing units of a different form;

FIG. 13 shows a cross-sectional view taken on the line 13-13 in FIG. 12;

FIGS. 14 and 15 illustrate fragmentary crosssectional views illustratingfurther details;

FIG. 16 shows a pressing station A in FIG. 12 in a side elevational viewat right angles to a length of belting being cured;

FIGS. 17, l8, l9 and 20 show diagrammatic crosssectional views taken onthe line l7l7 in FIG. 12 illustrating a sequence of movements duringoperation of a pressing station, and in which a series of clamps isindicated for maintaining pressure on an article being cured after thearticle emerges from the pressing station;

FIG. 21 is a longitudinal cross-section through a press unit otherwisesimilar to that of FIGS. 8 and 9, but designed to be spaced apart fromadjacent press units during a curing operation;

FIG. 22 is a vertical cross-section through a double daylight fixedpresses, two press units shown in position;

FIG. 23 is a representation of a stage in the course of continuouscuring ofa single length of conveyor belting using double daylight fixedpresses;

FIG. 24 is a representation of an elevation of the apparatus shown inFIG. 23.

The invention is described herein with particular reference to thecuring of conveyor belting, but as indicated above, the invention isapplicable to the curing of rubber and plastics and other elongatedarticles in general.

In the arrangement shown in FIG. 1 two identical presses 1 and 2 eachconsist of a number of identical press units, in the present example sixpress units, the units of press 1 extending between a first station S1and a second station S2 and being 18, 1C, 1D, 1E, 1F and 1G, and theunits of press 2 extending between a third station S3 and a fourthstation S4 and being 2B, 2C, 2D, 2E, 2F and 2G. The units of each pressare in contiguity with each other, i.e., in end-to-end contact, eachhave an upper platen (shown in FIGS. 1 to 4) and a lower platen (notshown), the two platens having means (not shown) to urge them towardseach other by hydraulic or other suitable power. Edge irons 3 areprovided for engagement with the edges of the belting and heating means(not shown), such as steam pipes, provided for raising the unit to asuitable curing temperature and maintaining it at that temperature. Atthe stage shown inFIG. 1 the pressure applied to urge together theplatens of units 16 and 26 which have just been added to the presses land 2 at the first and third stations 81 and S3 respectively, is lessthan that applied to the platens of the other units of the presses.

The conveyor belting 4 of press 1 consists of a series of portions; anuncured portion 4A which has not yet entered the press, a number ofportions (not shown) within the press units and a further portion 4B ofcured belting which has left the press. Similarly the conveyor belting 5of press 2 consists of an uncured portion 5A, portions (not shown)within the press units and a cured portion 58.

Fixed clamps 7 and 8 and longitudinally movable clamps 6 and 9 areprovided for producing and holding the longitudinal tension requiredduring curing. Similarly the tension means for the reinforcement ofbelting 4 consists of fixed clamps 11 and 12 and longitudinally movableclamps l and 13. Each clamp consists of a pair of horizontal jaws, oneof which is movable vertically by hydraulic or other means so that thejaws can be closed upon and hold the belt, or opened to allow the beltto pass between them. It will be seen that the fixed clamp of each pairis on the press side of each of the pairs of clamps.

The lower platens (which support the belting) are themselves carried onhorizontal tables (not shown in FIGS. 1 to 4). Fixed base members 14, 15are provided between the stations, on which press units can betransferred from the second station S2 to the third and from the fourthS4 to the first S1. In FIG. 1 press unit 1A, with its edge irons, issupported by fixed base member 14 and is in the course of beingtransferred from the second station S2 to the third station S3.Similarly press unit 2A, supported by fixed base member 15, is in thecourse of being transferred from the fourth station S4 to the firststation S1.

In FIG. 1 the tension in the reinforcement of the belting 4 is providedby clamps l0 and 13 which are shut firmly on the belting, clamps 11 and12 being open. Similarly, the tension in the reinforcement of belting isprovided by clamps 6 and 9 which are shut firmly on the belting, clamps7 and 8 being open. The arrow associated with clamps in FIG. 1 show themovement that took place in the immediately preceding step of themethod.

In FIG. 2 the presses l and 2 consist respectively of press units 1C,1D, 1E, 1F and 1G, and 2C, 2D, 2E, 2F and 2G (1G and 2G being stillpressedagainst the belting at a lower pressure than the other units).Press unit 28 has arrived at the fourth station S4, its platens havingbeen separated. The portion 16 of the belting from which unit 213 hasbeen released is in a fully cured condition. Similarly, press unit 18has arrived at the second station S2, the belting portion 17 being in afully cured condition. The press units 1A and 2A, which in FIG. 1 weresupported by turntables not shown in FIG. 1 but shown in FIG. 2 as 18and 19, have been turned through l on the turntables and forwardedrespectively towards the third and first stations, the upper and lowerplatens of each unit being situated respectively above and below thebelting but without yet being closed on the belting.

The belting 4 is now held in tension by clamps 11 and 12 while belting 5is held in tension by clamps 7 and 8. Clamps 10 and 13 have each beenmoved to the right, while in an open condition, and similarly clamps 6and 9 have been moved to the left while open. Clamps 10 and 6 eachinitially move a distancesomewhat less than the width of a press unit,the actual distance moved being such that when clamps l0 and 6, togetherwith clamps 13 and 9, are closed on 'the belting, and clamps 7, 8, l1and 12 are opened, clamps l0 and 6 are moved a further distance to bringthe total distance moved by these clamps up to that equalling the widthof a press unit, and at the same time applying the correct tension tothe belting 4 and 5. The relative proportions of the initial movementand the further movement are selected to provide the desired tension inthe belting.

With reference to FIG. 3, press 1 now consists of press units 1C, 1D,1E, 1F, 1G and 2A, and press 2 consists of press units 2C, 2D, 2E, 2F,26 and 1A, press units 1A and 2A having been added respectively to thetails of presses 2 and 1, their platens closed on the belting and theirtemperature raised. Press units 10 and 2G, which in FIG. 2 were shown asbeing at low pressure, now have that pressure increased to that of pressunits 1C, 1D, 1E and IF and units 2C, 2D, 2E and 2F respectively. Pressunits 1B and 2B have been forwarded respectively to turntables 18 and 19for rotation through l80 and if necessary change of side irons 20 and 21represent respectively the means for changing the edge irons of thepress units between successive curing operations thus making it possibleto use the press continuously without stopping production when one beltis completed and one of a different thickness and width is started andmaking it possible to press two different sizes of belt on the twopresses. The rotation is made to avoid the steam lines or otherconnections becoming crossed. The main steam line (not shown) feedingpresses l and 2 preferably lies between the two presses, and if rotationthrough of the press units being transferred were not made, it wouldresult in the steam lines of the transferred press units being on theouter side of the press with consequent inconvenience in operation.

As described previously, clamps 6 and 10 are shown as having been moveda further short distance respectively from clamps 7 and 11, as indicatedby the arrows touching clamps 6 and 10. Before this movement was madeclamps 6 and 10 were shut firmly on the belting and consequently thebelt portions 22 and 23 are subjected to a tension substantially thesame as the tension in the belting within the press. 24 and 25 representpreheating means to preheat the uncured belting before it is fed to thepresses and thereby to increase the output of the presses, but this isan optional feature and the success of the method of the invention isnot dependant upon it.

FIG. 4 shows the press units in the same order as shown in FIG. 3, butiron-changing means 20 and 21 and the heaters 24 and 25 are not shown.

The stage illustrated in FIG. 4 is that immediately following themovement (by means of hydraulic or other power) of belting 5 and itspress units 2C, 2D, 2E, 2F, 2G and 1A towards the right of the drawingby an amount equal to the width of a press unit. This movement has beenaccompanied by opening clamps 7 and 8 so as to release the belting andmoving clamps 6 and 9 towards the right by a distance equal to the widthof a press unit. Similarly, movement of the belting 4 and its pressunits 1C, 1D, 1E, 1F, 1G and 2A towards the left-hand side of thedrawing has been accompanied by opening clamps 11 and 12 and movingclamps l0 and 13 towards the left by a distance equal to the width of apress unit.

It will be seen that the disposition of the press units of presses 1 and2, the press units in transfer across the fixed base members 14 and 15and the tension clamps 6, 7, 8, 9, 10, 11, 12 and 13 is the same in FIG.4 as in FIG. 1 and that the cycle illustrated in FIGS. 1-4 has resultedin the emergence from the press of one fully cured portion of widthequal to the length of a single press unit. Consequently, the firststage of the next cycle of the method is represented by FIG. 2 and soon.

In the specific process described above each cycle results in the wholeof the belting portions within press units being cured to the sameextent and at any particular stage of the cycle the contiguous portionswithin the press units constituting the press at that time are in statesof cure which range from the almost fully cured state of the portion inthe press unit at the head of the press near stations S2 or S4 to astate of only very slight, if any, cure of the portion within the pressunit at the tail of the press near stations S1 or S3. It will be seen,therefore, that the conditions of temperature and pressure used toeffect cure are preferably selected so that a belting portion in anyparticular press unit reaches the fully cured state at the time when itspress unit is to be detached from the head of the press. Where thematerial being cured is one which is susceptible to over cure," care hasto be taken to select conditions which avoid that state.

If found convenient, the press units can move during transfer betweenpresses, on a semi-circular path between the two base members or on apath which is partly curved and partly straight. In that event, therotation of the units through 180 during transfer from the second orfourth to the third or first station respectively is effected by thecurved path and turntables can be dispensed with.

As shown in FIGS. 5 to 7 a press unit 26 comprises horizontalrectangular platens 27 and 28 between which is located a portion 29 ofconveyor belting. The press unit 26 further comprises insulation layers30 and 31 to reduce the loss of heat from the platens during curing andtables 32 and 33 which ensure a uniform compressive force on theconveyor belting during curing, the arrangmeent being such that theplatens are sandwiched between the insulating layers which arethemselves sandwiched between the tables.

The lower table 33 is supported by a support member 34 slidably locatedon rails 35 and 36 formed on fixed base member 37. The rails 35 and 36are located in corresponding grooves 38 and 39 formed in support member34, so that the whole press unit may slide along the fixed base member37 during curing. Motive power to cause the press unit to slide thus isderived from an external fluid pressure operated means and is applied tothe press units through drive brackets 40 and 41.

Upper table 32 is secured to two support brackets 42 and 43 extendingupwardly from the table having mounted at their upper ends axles 44 and45 one on each bracket, extending at right angles to the sides of thepress unit, two pairs of wheels 46 and 47 being rotatably mounted, onepair on each axle, to engage overhead guide rails (not shown) at secondstation S2 or fourth station S4 at the end of a curing operation.

To control the width and thickness of the portion of belting 29 beingcured, and to produce straight edges thereon, the press unit 26 isprovided with two edge irons 48 in the form of plates having straightedges and adapted to be positioned with one edge of each iron inengagement with one edge of the portion of belting 29. The edge ironseach have formed therein two openings 49 to provide locating sockets forfluid pressure operated means (not shown) to urge the irons intoengagement with the belting, two series of apertures 50 being providedto co-operate with pins 51 associated with the upper platen 27 to holdthe edge irons in the required position after engagement with thebelting as described above. Two further apertures 52 in the form ofslots adjacent each end of the iron are provided for a purpose to bedescribed.

The press unit 26 is provided with four similar piston and cylinderassemblies 53 operable by fluid pressure to draw together the twoplatens, thereby exerting compressive forces on the belting 29 beingcured. The piston and cylinder assemblies are all mounted on the upperrectangular table 32, one near each corner thereof in order that atleast one assembly should be located adjacent each edge of the oppositeside edges 54 and 55 (FIG. 5) of the upper platen 27.

Each piston and cylinder assembly 53 comprises a piston rod 56 attachedat one end to a piston (not shown) and having an abutment 57 at theother end, the piston rod being arranged to extend through the apertures52 formed in the edge irons 48, and corresponding alignable apertures inthe tables 32, 33, insulation layers 30, 31, platens 27, 28 and thesupport member 34.

In FIG. 5, the piston rod 56 is shown fully extended outwardly from thecylinder. In order that, on admission of fluid pressure to the cylinderand withdrawal of the piston rod into the cylinder, the platens may beurged together, removable means in the form of a swingable locking piece58A (only one being shown in FIG. 6) is provided for each piston andcylinder assembly to engage the abutment 57 and prevent withdrawalthereof so that the tables 32, 33 and thereby the platens 27, 28 aresqueezed between the cylinders and the abutments of the assemblies 53.

Control panels 59 and 60, one on each side of the press unit 26 areprovided to control the supply of fluid pressure to the variouscylinders on the unit, valves (not shown) on the panels being operatedby rods and cams (not shown) at appropriate points in the course of anygiven curing operation.

The various connections necessary for the supply of steam, cold water,hydraulic power and other requirements to the press units are made tothe inner side of the press units with respect to the closed circuitpath which they follow, by means of flexible pipes (not shown) and aservices conveyor.

In the apparatus shown in FIGS. to 7 adjacent press units are securedend-to-end during curing of the belting by means of two fluid-operatedlatch mechanisms 61 on each press unit, mounted horizontally, one oneach side edge of each table adjacent one end of each side edge. Eachlatch mechanism comprises a hinge 62 on which a cylinder 63 is mounted,swingable in the plane of the table. A piston (not shown) is located ineach cylinder 63, and has a piston rod 64 with an abutment 65 at thefree end thereof. Each latch mechanism further comprisesa latch portion66 in the form of two separate raised members 67 arranged so that pistonrod 64 can pass between them by swinging cylinder 63 on hinge 62. Whenfluid pressure is supplied to cylinder 63, the piston is urged towardthe hinge end of the cylinder 63, and abutment member 65 engages raisedmembers 67 of the adjacent press unit 68 thereby urging the unitstogether.

Edge irons 48 are each provided with a rectangular guide slot 69extending parallel to the end edges of the edge iron, in each of whichis located a corresponding guide lug 70 attached to lower platen 28,this provision being to ensure that the edge irons are always positionedparallel to the side edges of the platens, thereby ensuringsubstantially straight edges are formed on the belt through-out itslength. 7

A curing operation employing the apparatus shown in FIGS. 1 to 7 willnow be described.

In FIG. 1, press unit 1A, which for the purpose of describing thissequence of operations will be considered to be the press unit 26 ofFIG. 7, but as will be explained more fully hereafter may be of amodified design, is shown midway between the second station S2 and thethird station S3. At this point unit LA is turned through an angle of180 on turntable 18 (FIG. 2) and then is moved towards station S3 wherethe belting 5A is located between platens 27 and 28. Unit 1A then movesup to unit 2G as shown in FIG. 2, latch mechanism 61 secures it to unit2G and edge irons 48 engage the sides of the belt, and are located inposition by pins 51. Assemblies 53 close the platens on the belt underlow pressure. The platens, being continuously steamheated are alreadyhot, and curing begins. Curing proceeds under increasing pressure frompiston and cylinder assemblies 53 as the belt and attached press unitsmove slidably and stepwise through the press supported on the fixedguide member 37 as already described, in conjunction with theappropriate clamping operations of clamps 6, 7, 8, 9, 10, ll, 12 and 13.

During curing, appropriate adjustments to fluid pressures and othercontrol operations are effected by engagement of the controls of panels59 and 60, for example by levers and earns suitably positioned as thepress unit slides along fixed base member 37.

As unit 1A reaches station S4, the pressure on the platens is released,the latch mechanism disengaged, the edge irons released, and wheels 46and 47 engage fixed overhead guide rails (not shown) causing the upperpart of the press unit to be disengaged from the belt. The parts of thepress unit are then moved sideways, to station S1, being turned throughan angle of 180 during such movement, ready to engage with the belt 4,thus completing one curing operation.

FIGS. 8 and 9 show a modified press unit arranged to be heatedintermittently and used in conjunction with means independent of thepress unit for applying a suitable compressive force to the belt.

As previously described, pressure is applied to the platensprogressively, in that initially the pressure is relatively low, thenbeing increased up to a maximum compressive force which is set byvarious requirements, for example to squeeze the rubber into theinterstices of the tensile member, and to produce a uniform surface.However, it has been found that this maximum compressive force need notbe applied throughout the remaining curing time of the belting. It issufficient for the compressive force to be built up during the firstpart of the curing cycle, and may be reduced thereafter for theremainder of the operation, to a magnitude sufficient to overcomepressure produced between the platens, for example by the formation ofsteam from moisture present in the article being cured.

It is therefore possible to pass the press units, one at a time, througha fixed press which builds up the maximum compressive force on the pressunits, after which latches are engaged, to lock the platens together.The press units then pass from the press, the latches retaining theplatens together and thus maintaining pressure on the belt. Dependingupon the material being cured, there may be a variation in the pressurebetween the platens, and this pressure may even reduce to zero by theend of the cycle.

While such fixed presses need to be of substantial construction, as theyonly have to accept one press unit at a time the size of the fixedpresses can be much smaller than conventional belting presses.

FIGS. 8 and 9 illustrate a press unit, 71 for use with a fixed press andfor intermittent heating. Press unit 71 comprises platens 72 and 73between which is located a portion 74 of a length of conveyor belting.Edge irons 75 similar to the irons 48 employed in the press 26 depictedin FIGS. 5 to 7 are provided, with edge iron pins 76 associated withupper platen 72 co-operating with a series of apertures (not shown)formed in each edge iron as previously described in connection with edgeirons 48.

Lower platen 73 is provided with a pair of rightangled mild steel angles77 one limb of each of which is secured to one side edge face of theplaten. The other limb extends laterally from the platen 73, with itsupper surface in the same plance as that of the belt-contacting surfaceof platen 73.

A second pair of right-angled mild steel angles 78 of smaller gaugemetal then the angles 77 is located in the angle between the limbs ofthe angles 77, and between the angles 77 and the angles 78 is aright-angled section layer of insulating material 79, to minimise theloss of heat from the platen. The assembly of platen angles andinsulation material being secured together to form a unified structure.

Mild steel angles 78 serve as guide and support sur faces for the pressunit and engage guide wheels 80 rotatable in a horizontal plane, andsupport wheels 81 rotatable in a vertical plane mounted on right-angledsupport brackets 82 fixed to and extending along the length of the presswith a base 83. Between support brackets 82, and fixed to base 83 is alayer of insulation 84, the arrangement being such that the platens aresupported by support wheels 81 so that there is an air gap between theupper surface of insulation layer 84 and the lower surface of platen 73.

Upper platen 72 is also provided with a pair of rightangled mild steelangles 85 corresponding to the angles 77, one limb of each of which issecured to one side edge face of the platen 72, the other limb extendinglatv erally with its lower surface in the plane of the beltingcontacting surface of platen 72.

The platens 72 and 73 of press unit 71 are of such a thickness thattheir thermal capacity is sufficient for the curing of the belt in thetime of the curing cycle, without requiring any further addition ofheat. For example it has been found that the thermal capacity of a3-inch thick platen is more than sufficient for the purpose ofvulcanising a l-inch thick belt.

Heat is supplied to the platens at re-heat stations by bringing theplatens into contact with hot metal plates as will be describedhereafter. Other satisfactory methods of re-heating the platens includethe use of infrared heating units and direct heating by gas flames ofthe outer surfaces of the platens which surfaces do not contact articlesto be cured.

Employment of an intermittent supply of heat has the advantage thatbefore the platen is brought into contact with the article to be cured,it can be heated to a temperature higher than that normally used for thecuring of the article so that heat penetrates from the surface of thearticle to its centre portion more quickly, thus providing a shortercuring time. The loss of heat from the surface of the platen to thearticle cools the platen surface so that over-curing of the article canbe avoided.

As press unit 71 moves along the press in the course of a curingoperation, heat losses from the upper surface of upper platen 72 areminimised by the provision of a stationary canopy 86 extending alongmost of the length of the press and having a lining 87 of insulatingmaterial.

Two lifting lugs 88 are secured to each angle 85 at the side of pressunit 71 whereby the upper platen may be lowered and lifted by externalmeans (not shown) as required to engage and disengage the belting 75 atthe beginning and end of a curing operation.

A sequence of operations during curing, employing press units as alreadydescribed with reference to FIGS. 8 and 9 and fixed presses 89 whichincorporate platen reheating apparatus (see FIG. 10) will now bedescribed with reference to FIG. 11.

In Flg. 11 the arrangement and general mode of operation of press units71 (only one being numbered), clamps 90 for tensioning the belts 91 and92 and preheat stations 93 for pre-heating the belt are as previouslydescribed with reference to FIGS. 1 to 4.

At the first station S1 in FIG. 11, the belt 91 is located between theplatens 72 and 73 of press units 71 (FIG. 10). Edge irons engage theedges of the belt and the press unit is secured to its adjacent unit byscrewthreaded unit clamping means 100 operated by external means.Locating pins 101, one on each side of each press unit and passingthrough apertures formed in angles 77 and 85 ensure accurate alignmentof the platens. The press unit is then moved on wheels 81 and guided bywheels 82 to fixed press 89 (see FIG. 10)

where by operation of piston and cylinder assembly 94 mounted on base95, movable lower table 96 slidably mounted on guide members 97 is urgedtowards upper table 98 thereby causing hot plates 99, insulated from thetables by insulating layers 102, to engage the platens and the pressunit to be lifted off wheels 81.

While the press unit 71 is under compression in fixed press 89, platenclamping means in the form of four platen clamping screws 103, two ateach side edge of the press unit and passing through angles 77 and 85,are operated by external means so that on emergence of the press unitfrom the fixed press the platens are retained at substantially theproximity they assumed in the fixed press.

After a predetermined interval the press unit leaves the fixed press 89and moves in stages in a manner similar to that already described inconnection with FIGS. 1 to 4, towards the second station S2. Curingcontinues as heat is conducted from the platens to the portion ofbelting with which they are engaged, while the unit rides along onsupporting wheels 81 under the canopy 86.

At the second station the unit is released from its adjacent unit byreleasing the unit clamping means 100, compression is released byreleasing clamping screws 103, and locating pins 101 and edge iron pins76 are disengaged all by external means (not shown), and the upperplaten lifted away from the belt by means of lugs 88. The lower part ofthe unit is moved away from the belt, and the whole unit transferred tothe third station S3 but without being turned round since this isunnecessary because no flexible connections such as steam pipes are madeto the press unit. At the third station S3, the sequence of operationsjust described is repeated and the press unit moves with the belt 92 tothe fourth station and thence back to the first station again.

As previously stated, where curing certain articles of a plasticconsistency, there is a tendency for material to be squeezed out frombetween the platens, at the rear end of the press unit. FIGS. 12 to 22illustrate an embodiment of the invention in which pressure is appliedby the press units to successive contiguous portions of the articlebeing cured, in such a manner that pressure is applied, or increased, inthe rearward zone of one portion as pressure is applied to the forwardzone of the next succeeding portion. The press units are arranged sothat successive platens are in end contact with one another, andsqueezing out of material is thus avoided.

As seen in FIG. 12, there are first and second identical curing units201. 202 each comprising a plurality of identical press units 203extending between two stations in contiguous head to tail relationshipand in engagement with respective portions of reinforced rubber conveyorbelting.

The press units 203 are successively brought into alignment with alength of belting 204 at a position 205, and successively engaged withsuccessive contiguous portions of the length of belting 204 at apressing station 225 constituting a first station of the first curingunit 201 and move in engagement with the belting to a second station 206at the other end of the first curing unit where they are successivelydisengaged from the belting and transferred through a position 207 to apressing station 225 constituting a first station of the second curingunit 202. Here the press units are successively engaged with successivecontiguous portions of another length of belting 208 and moved inengagement with the belting to a second station 209 at the other end ofthe second curing unit where they are then successively disengaged fromthe belting and returned to the position indicated by numeral 205 tocommence another identical sequence of operations.

As shown in FIG. 13, each press unit 203 comprises a pair of thick metalplatens 210, 211 for engagement with the belting 204 and 208. Holdingmeans in the form of a series of clamps (not shown) are moved to preventseparation of the platens and thereby maintain any desired compressiveforces on the belting during a curing operation as the press unit passesbetween the first and second stations of the two curing units 201 and202.

To control the width and thickness of the portion of belting being curedby each press unit 203 and to produce straight edges on the belting,each press unit is provided with two edge irons 212 in the form of metalslats have straight side edges and arranged to be posi tioned with oneedge of each iron in engagement with one edge of its respective portionof belting. Angle members 214 are attached to the sides of the platens210, 211 to provide support and location for the edge irons.

Power operated means (not shown) independent of the press units isprovided to force the edge irons 212 into engagement with the edges ofthe belting after the platens 210, 211 have engaged the belt at thecommencement of each curing operation at the first stations 225. Tomaintain the separation of the edge irons and therefore to control thewidth of the belting throughout each curing operation, each press unitis provided with locking means for the edge irons comprising a pair oflocking pins 213 (see FIG. 14) mounted at each side of the press unit,each pin being seated in aligned holes formed in a first pair of rightangled mild steel angles 214. The mild steel angles are secured inback-to-back relation, one to each side edge of each platen so that inthe assembled state of the platens they constitute a T-shaped structure,the pins 213 being seated in holes formed in the two limbs one from eachmild steel angle, which are back-to-back.

Each locking pin 213 is locatable in any one of a series of aperturesformed in its associated edge iron 212 at a corresponding position alongthe length thereof, the apertures of each series being spaced apartacross the width of the edge iron. When the edge irons have been forcedto have their required separation at the first station 225, they aremaintained at this separation by locating the locking pins in theapertures in the edge irons appropriate to this separation.

Generally, in other respects, the press units 203 are similar in form tothe press units 71 illustrated in FIGS. 8 and 9, and therefore furtherdetailed descriptions of the press units 203 is not considerednecessary.

Two iron change units 215 are provided between the two curing units 201,202, one at each end thereof, where the edge irons required in thecuring of one belt are changed, if necessary, for those required for theother belt. Thus, if desired, the two belts 204 and 208 may be ofdifferent widths and thickness.

As each belt passes through its respective curing unit, it is maintainedunder a predetermined steady longitudinal tensile load by means oftension units 216 located one at each end of each press.

Each tension unit 216 comprises a longitudinally fixed clamp 218, 219,and a longitudinally movable clamp 217, 220. By engagement of the clampswith and disengagement of the clamps from the belt and movement of themovable clamps, at appropriate times, the belt is moved stepwise throughthe curing unit under substantially constant tension.

The operation of the clamps of the tensioning units 216, is as theoperation of the clamps 6 to 13 of the arrangement illustrated in FIGS.1 to 4 and will not be further described, it being understood that thepurpose of the units 216 is to provide for tensioning of the belting 204and 208, and maintaining such tension, while permitting movement of thebelting through the curing units 201 and 202.

To support and guide the press units for longitudinal movement with thebelting during curing, support and guide wheels are provided at spacedapart positions along both sides of each press. The support wheels 221(see FIG. 13) are mounted for rotation about horizontal axes parallel tothe planes in which the press unit platens 210, 211 lie and engagesupport surfaces extending along the length of each press unit, one ofeach side thereof. Guide wheels (not shown) are mounted for rotationabout vertical axes and engage guide surfaces also extending along thelength of each press unit one on each side thereof.

To support and guide the press units for longitudinal movement with thebelting during curing, support and guide wheels are provided at spacedapart positions along both sides of each press. The support wheels 221(see FIG. 13) are mounted for rotation about horizontal axes parallel tothe planes in which the press unit platens 210, 211 lie andengagesupport surfaces extending along the length of each press unit, one oneach side thereof, whereas the guide wheels 222 (see FIG. 15) aremounted for rotation about vertical axes and engage guide surfaces alsoextending along the length of each press unit one on each side thereof.

The support and guide surfaces of each press unit are constituted by asecond pair of angle members 223 mounted one of each side of the lowerplaten 211 of each press unit 203 and insulated from the first mildsteel angle 214 secured thereto, by a layer 224 of insulating material.

Similar means is provided for supporting and guiding the press units 203during transfer from one curing unit to the other.

The pressing stations 225, which respectively constitute the firststation of each curing unit will now be described.

As shown in FIG. 16, each pressing station 225 comprises thrust meansfor simultaneously applying pressure through three successive pressunits within the pressing station to three contiguous portions of thebelting. It is sufficient however, for the success of the invention fora pressing station to accommodate only two press units as will beexplained hereafter.

The thrust means comprises a vertically movable base member designatedas a whole by the reference numeral 226 and equal in length to threepress units, on which the platens of three press units are supportedwhile in the pressing station, and first and second vertically movablepress heads each designated as a whole by the respective referencenumerals 227, 228. The vertical movement of the base member 226 liftsthe press units off their support wheels 221 (not shown in FIG. 16) sothat the wheels are not subjected to loads arising from the pressureapplied to the belting in the pressing station. Pressure is applied tothe belting within the three press units by vertically downward movementof the press heads 227, 228.

The press heads 227, 228 are fluid pressure operated. The first presshead 227 comprises two portions, a parallel portion 243 and a taperedportion 242. Each portion is approximately equal in length to one pressunit and the tapered portion 242 is at the end at which the beltingenters. Mounted below the press head 227 are two pressure plates 230 and231. The pressure plates are in two parts, an upper part and a lowerpart, the lower part being heated and insulated from the upper part by alayer of insulation 247. The pressure plates 230 and 231 are of the samethickness and are of constant thickness.

Mounted below press head 228 and rigidly attached thereto is a pressureplate 228a, comprised of two parts, upper and lower, separated by aninsulation layer 247. The overall thickness of press head 288 andpressure plate 228a is the same as that of the parallel portion 243 ofthe press head 227 plus pressure plate 231.

The manner in which the two pressure plates 230, 231 of the first presshead are mounted below will now be described:

At the end of the first press head 227 at which the belt 204 enters thepressing station, the rearward end of the first pressure plate 230 ispivotally connected to the first press head 227 by a link joint at eachside thereof, each link joint comprising two hinge members 232 onerigidly secured to the first pressure plate and the other rigidlysecured to the press head and a rigid link 233 interconnecting the twohinge members and pivotally secured thereto at each end.

Three pairs of side plates 234, 235, 236 are rigidly secured one plateto each side of the first and second pressure plates 230 and 231 and oneplate to each side of the second pressure plate 228a respectively.

The side plates 234, 235, 236 extend downwardly to the level of the belt204 being cured, where they are pivotally interconnected, as describedbelow.

The rearward ends 237 of the side plates 236 of the pressure plate 228aare pivotally connected to the forward ends 238 of the side plates ofthe second pressure plate 23.1 of the first press head 227. The pivot isat the level of the belting but this can be varied as described later.Thus a downward movement of the second press head 228 effects a similardownward movement of the forward end of the second pressure plate 231 ofthe first press head 227.

The rearward ends 239 of the side plates 235 of the second pressureplate 231 of the first press head 227 are pivotally connected to theforward ends 240 of the side plates 234, of the first pressure plate 230of the first press head, and the two joints therebetween are eachsupported by a support arm 241 pivotally connected at one end to the twoside plates 234, 235 atthe joint therebetween, and pivotally connectedat its other end to the upper tapered thrust member midway along thelength thereof.

The first and second pressure plates 230, 231 positioned below thetapered and parallel portions 242 and 243 respectively, are each of thesame length as one press unit, so that for a given downward movement ofthe first press head 227, the second pressure plate 231 will experiencea generally uniform thrust over .its

whole upper surface, whereas although the first pressure plate 230 willreceive substantially the same thrust at its forward end as the secondpressure plate, the thrust decreases towards the rearward end of thefirst pressure plate where it is comparatively small. As a result of thepivotal mounting of the said first and second pressure plates, thedownward thrusts applied to the upper platens 10 of the press unitsbelow the two pressure plates correspond to the thrusts received by thetwo pressure plates themselves.

To ensure that the links 233 only support the pressure plate 230 and donot apply any pressure thrusts on actuation of the press head 227, whenthe press head 227 is raised there is a small gap between the topsurface of the pressure plate 230 and the undersurface of the press head227. Also one of the pairs of hinge members 232 has the pivot holesslightly elongated to allow some vertical movement between the pressureplate 230 and thepress head 227.

The second press head 228 applies a substantially uniform thrust to theupper platen 210 of its respective press unit.

To allow the pivotal movements of the two pressure plates, 230, 231 ofthe first press head 227, forward and rearward edges of the pressureplates are spaced apart as shown in FIG. 16. Alternatively they can bechamferred.

The operation of the pressing stations will now be described withreference to FIGS. 17 to 20 of the drawings. FIGS. 17 to 20 are purelydiagrammatic and many parts shown in FIG. 16 have been omitted forclarity.

The belting 204 and press units compressing platens 210, 211 movestepwise through the pressing stations 225, moving forward by the lengthof one press unit in each step, the two press heads 227, 228 executingone complete downward and upward movement before the belt and pressunits move on.

FIG. 17 illustrates the situation with both press heads raised and thebelting and press units having moved forward the distance of one pressunit. When the belting and press units are correctly positioned, thepress heads come down into contact with the press units (FIG. 18). Onfurther movement of the press heads, press unit C and its respectiveportion of uncured belting is compressed first between the firstpressure plate 230 and the base member 226 (see FIG. 19). This causesthe belting 204 to achieve at the forward end of the press unit C thethickness required in the fully cured belting, but at the rearward endthe belting is hardly compressed, if at all.

Next, the pressing station is opened and the press unit C, with thebelting, is moved one press unit length further into the pressingstation (see FIG. 20) to the position of press unit B in FIG. 17, and afurther press unit D takes its place between the first pressure plateand the base member.

It is believed that it is not necessary for this specification toinclude drawings showing the press unit C undergoing the next stage ofcompression in the pressing station, because press unit C is then asshown in FIG. 20, in the position occupied by press unit B in FIGS. 17to 19, and undergoes the sequence of operations executed on press unit Bin FIGS. 17 to 19. Accordingly, this next stage will be described withreference to press unit B in FIGS. 17 to 19.

When the first press head 227 is forced downwardly, as shown in FIGS. 18and 19, the press unit B is compressed at its rearward end substantiallysimultaneously with the initial exertion of compressive forces on thenext following contiguous portion of belting by the forward end of thenext following press unit.

Thus the belting within the press unit B is brought to its requiredfinal thickness at the stage illustrated in FIG. 19, and clamps aresuitably tightened to maintain the desired compressive forces on thebelting.

Since the initial exertion of appreciable compressive forces at therearward end of the press unit within the pressing station does notoccur until the press unit is positioned below the second pressure plate231 of the first press head 227 (see press unit B in FIGS. 18 and 19),and this occurs substantially simultaneously with the initial exertionof compressive forces on the'forward end of the next following pressunit (see press unit C in FIG. 18 and 19), the tendency for soft hotrubber to be squeezed out from between the platens at the rearward endof the press unit is smaller than when there is no simultaneouscompression at the forward end of the next following press unit.

On commencing curing of a length of belting, some rubber may tend to besqueezed out from between the forward ends of the platens of the firstpress unit on the belt, but if this occurs the short length of affectedbelting can be discarded and from then onward the problem will not ariseagain with the remainder of that length of belting.

The second press head 228 engages each press unit 203 successively butsince the belting in the press units has by then already been subjectedto substantially the required degree of compression, very little or nofurther compression occurs at this stage. However, by virtue of thearrangement of the pivoted side plates 234, 235, 236, the forward end ofthe second pressure plate 231 of the first press head 227 is always atsubstantially the same distance from the base member 226 of the pressingstation as the second press head 228 and therefore during the initialexertion of compressive forces on the rearward end of any given pressunit, the compressive forces at the forward end thereof are maintainedand there is no tendency for soft hot rubber to be squeezed in a forwarddirection in this stage.

The second press head 2 28 constitutes means, independent of the firstpress head 227 to urge the forward end of the second pressure plate 231towards the belting being cured, and the maintenance, when required, ofcompressive forces at the forward end of each press unit is the mainfunction of the second press head. Accordingly if desired the secondpress head can be dispensed with and replaced by equivalent means suchas fluid pressure operated ram acting on the forward ends of the sideplates 235 of the second pressure plate 231. However, the second presshead 228 does also serve to maintain uniform compressive forces over thewhole area of belting within the press unit which is engaged by thesecond press head at any given time. Thus, provision of the second presshead allows the clamps which are provided for each press unit to be ofrelatively light construction, and to be designed to act on the pressunit platens around the edges thereof only. Although such clamps areadequate to maintain pressure on the belting after it has passed throughthe pressing station, on their own the clamps would be incapable ofmaintaining uniform pressure on a portion of belting when the precedingcontiguous portion of belting is being compressed in a pressing station,since in such circumstances the pressure of hot fluid rubber can besufficient to cause buckling of the platens of a press unit which isclamped only at its edges.

Further, by holding its associated press unit in firm head to tailrelationship with the next following press unit, the second press head228 also serves to prevent the two press units separating longitudinallyunder the pressures of hot fluid rubber and thereby effectivelystretching the belting. Thus the inclusion of a second press head in thepressing stations although not essential is nevertheless desirable.

Heat is supplied to the platens of the press units during the time thatthey are under compression in the pressing stations 225, so that eachpress unit is reheated at the beginning of each curing operation.

The heat is transferred to the platens of the press units by contactbetween the platens and heated portions of the thrust means. Thuscertain portions of both the base member 226 and the press heads 227,228 are continuously heated by electricity, steam, or any otherconvenient source of heat. The supply of heat to two press heads and tothe base member is limited to the lower portions and upper portionsrespectively thereof, which engage the press units. The heated portionsof the press heads are insulated from the remainder thereof byinsulation layers 247, as previously described, to minimise heat loss,and a similar insulation layer 248 is provided below the heated portionof the base member.

Heat losses from the press units on emerging from the pressing station225 during a curing operation are minimised by providing tunnels 249each having a lining 250 of insulating material (see FIG. 13). Thetunnels closely surround the press units and extend along the length oftheir respective curing unit 201, 202 so that the press units passtherethrough during each curing operation.

The supply 251 (FIG. 12) of uncured belting at one end of each curingunit may be simply in the form of a roll of uncured belting mounted forrotation on an axle, or, the curing unit may be positioned at one end ofa belting production line in which case the uncured belting enters thepress immediately after it has been assembled from, for example, arubber-frictioned textile reinforcement and superimposed rubber coveringlayers.

On emerging from its respective curing unit the belting passes through atrim unit 252 (FIG. 12) for the removal of rubber flashing, and aftercooling is ready for service.

If it is found desirable, a reheating station 253 (see FIG. 12) may beprovided near the end of each curing unit to supply heat to the platensof the press units shortly before the press units reach the secondstation of the respective curing unit and are removed from the belting.Heat is supplied to the platens of the press units in the reheatingstations by contact between the platens and heated metal blocks.

Also, leakage of soft hot rubber from between the forward and rearwardends of the press units may be further reduced by the provision of twosteel bands (not shown) of the same width as the belt, sandwiching thebelt between them during curing and moving along the press with thebelting. Thus, pressure is applied to the belting through the steelbands by the platen of the press units. The belts are at all timessupported for their full area by the pressure plates.

Each steel band is in the form of an endless loop which is held in thecorrect position relative to the belting by the press units and which onemerging from the press with the cured belting is guided back to theother end of the press by large diameter pulleys or rollers.

Alternatively, instead of the steel bands described above, means may beprovided for positively forcing the platens of successive press unitstogether in a longitudinal direction so that the forward end of onepress unit is more firmly engaged with the rearward end of the nextpress unit and so on, so that leakage of rubber between the said ends isminimised. This may be achieved simply by arranging that the pivotaljoints between the side plates 236 of the second press head 228 and theside plates 235 of the second pressure plate 231 of the first press head227 are higher with respect to the base member 226 than thecorresponding joints between the side plates of the two pressure plates230, 231 of the first press head.

The advantages provided by the modifications, as described above inrelation to FIGS. 12 to 20 is as follows:

First, by reducing or eliminating the squeezing out of soft hot rubberfrom between the platens of the press units at the forward and rearwardedges thereof the operation of the press as a whole is improved sincerubber squeezed out from one press unit tends to interfere with theoperation of adjoining press units. Further the quality of the curedarticle produced by the curing units is improved, since formation ofirregularities and ribs on the surfaces thereof by rubber squeezed outfrom between the platens, is avoided.

Secondly, because there is a gradual transition from small or zerocompressive forces at one end of a pressing station to relatively largecompressive forces at the other end thereof, an appreciable step in beltthickness is never formed by the curing units as it is in conventionalbelt presses, and therefore kinking of the belt reinforcement andassociated irregularities in the belt surface are avoided.

The use of steel bands sandwiching the belt between them to reducefurther the leakage of soft hot rubber from between the press unitplatens and to give an improved finish to the belt, is associated withthe advantage referred to in the preceding paragraph. Such steel bandscannot be employed in presses where any appreciable step in beltthickness is produced during curing, since such a step would causekinking of the steel bands which would rapidly become useless.

The present abutting forward allows such steel bands to be used, andwhen they are used they eliminate the formation of thin films of rubberflashing on the upper and lower surfaces of the belt through leakage ofrubber between the abuttingforward and rearward edges of the platens ofsuccessive press units which might occur. Unlike the rubber flashingwhich is formed at the edges of the belt as a result of rubber leakingbetween the platens and the edge irons, which is easily removed in thetrim units, films of rubber on the upper and lower surfaces of the beltare not easily removed and therefore it is a clear advantage to avoidtheir formation.

The press unit 304 shown in FIG. 21 is designed for use in the apparatusrepresented in FIGS. 23 and 24, using the double daylight fixed press ofFIG. 22. This apparatus is intended to be used where it is notconvenient to provide for simultaneous cure two belts having more orless the same curing time and length, as is desirable for the apparatusdescribed above. The press unit 304 is a modification of the press unit71 of FIGS. 8 and 9 in that it is arranged so that during a curingoperation units of this type are spaced apart from one another along alength of the article being cured. Consequently there is noscrew-threaded unit clamping means corresponding to that of press unit71 (FIG. 9). At each end of press unit 304 there are provided foursubstantially L-shaped end pieces 305, each secured to an end surface ofone of the platens through an intermediary insulation layer 306 by oneof the limbs of the L, the other limb serving to extend longitudinallyof the belt contacting surface of the platen but being shaped so thatthese extended surfaces provided by adjacent end pieces slope away fromeach other.

Insulated from the hot platens by the insulating layers 306, the endpieces 305 remain relatively cold (water cooling being used ifrequired), and thereby ensure that at each end of the press unit, thereis a strip 307 of the belt, extending across the belt which is undercompression but which is substantially unheated thus preventing hotviscous rubber from being squeezed out from the ends of the unit andavoiding consequent irregularities on the surface of the belt at theends of the press unit.

Other features of press unit 304 are substantially the same in structureand function as those of press unit 71 of FIGS. 8 and 9 and are numberedaccordingly.

Fixed press 308 comprises a horizontal base 309, side members 310secured thereto in vertical positions, a fixed upper table 311 securedto the upper ends of side members 310, an upper moving table 312 and alower moving table 313 both slidably located on side members 310 betweenthe base and the fixed upper table, and a fluid-operated piston andcylinder assembly 314 located between the lower moving table and thebase.

As shown in FIGS. 23 and 24 the belt 315 extends in an upper run throughtensioning clamps 316, belt preheat station 317, a first station S1, theupper daylight of double daylight fixed press 308, through a secondstation S2 to rollers 318, and in a lower run from rollers 318 throughpre-heat station 319, third station $3, the lower daylight of doubledaylight fixed press 308 through fourth station S4 and tensioning clamps320. Thus the first and second stations are at one level and the thirdand fourth stations at another level and the belt is arranged to move intwo runs, one above the other, one run between the first and secondstations and the other run between the third and fourth stations.

Tensioning clamps 316 and 320 operate in the same way as clamps 6, 7, 8and 9 of FIGS. 1 to 4. On engaging the belt at station S1 press unit 304with pre-heated platens moves to the upper daylight of fixed press 308where it is compressed by operation of piston and cylinder assembly 314and its platens clamped together. The press unit then moves stepwise tostation S2 where it is disengaged from the belt, transferred laterallyto iron charging station 321 and then to re-heat station 322 which is atthe level of the lower run of the belt where its platens are re-heated.At station S3 it engages a substantially uncured portion of the belt305, thereby filling in an uncured gap, passes to the lower daylight offixed press 308 where it is compressed again, its platens clampedtogether and it begins another curing operation. At station S4 the pressunit is again disengaged from the belt and transferred via iron chargingstation 323 and re-heat station 324 to the upper run and back to stationS1, where another cycle of operations begins.

1. A curing press unit for curing elongated articles comprising aplurality of press units each having a pair of platens, a first stationhaving press means for bringing press units in curing relationship withsuccessive portions of an article to be cured, means for moving pressunits in curing relationship with an article to be cured in a stepwisemanner through the curing unit, a second station for succesively movingthe press units out of curing relationhip with the article at a secondstation, means for the press unit to move the platens of two successivepress units in a direction perpendicular to the surface of an articlebeing cured in such a manner that in a first stage of operation of thepress means the forward end of a platen of one press unit is pressedagainst said article so as to incline the platen relative to thelongitudinal direction of the article, and in a second stage ofoperation of the press means the rearward end of said platen is pressedagainst said article to dispose said platen parallel to the other platenof the pair of platens, the press means having means such thatsimultaneous with the second stage of operation the neighboring forwardend of a platen of the next successive unit is pressed against saidarticle.
 2. A curing press unit according to claim 1 in which the pressmeans comprises first and second pressure plates for engagement with twosuccessive press units, the pressure plates being pivotally mounted sothat the forward end of each pressure plate can be moved towards thearticle being cured independently of the rearward end thereof.
 3. Acuring unit according to claim 2 in which the press means comprises athrust member for urging the pressure plates into engagement with thepress units, the thrust member comprising a tapered portion forengagement with the first pressure plate and an untapered portion forengagement with the second pressure plate, and auxiliary press meansbeing provided independent of the tapered thrust member to urge theforward end of the second pressure plate towards the article beingcured.
 4. A curing unit according to claim 3 in which the auxiliarypress means comprises a press head pivotally connected to the forwardend of the second pressure plate and arranged to exert a substantiallyuniform compressive thrust on the press unit immediately ahead of thepress unit engaged by the second pressure plate.